The invention relates to an arrangement within a Yankee cylinder or the like and a roller of a paper machine, particularly in order to improve the runability, to solve linting problems and thus to reduce production disturbances, and to improve the fire safety of the paper machine.
In a paper machine a Yankee cylinder dryer and a hood connected to it are generally used to dry a paper web, whereby hot air is blown at a high speed from the hood against the paper web on the surface of the cylinder in order to improve the drying effect. The paper web is detached from the cylinder's surface with the aid of a doctor blade. Already in this phase a substantial amount of lint comes off the paper, particularly from soft tissue. The paper is conveyed with the aid of mechanical conveying equipment to the roller, and also in this phase lint will come off the paper. At the roller a part of the lint will stay within the roll being made, but a part of the lint is lost to the surrounding air, which is hot and flows strongly upwards spreading the lint further into the paper machine room.
As the speed of the paper web is quite high, usually at least 1500 m/min, even over 2000 m/min, the created amount of lint is quite high. Due to the high speed, fibres and other particles will quite easily come off the paper. Moreover, due to the high speed the lint will get a quite high speed in the air flow, and therefore it will be spread effectively. The lint has many harmful effects. It will accumulate as a layer on the surfaces of structures, particularly on other than vertical surfaces. The lint may come off the surfaces as lumps and fall down on the paper web so that it causes a production break. The lint may even catch fire, because a part of the equipment is very hot, in spite of the insulations. Thus a part of the paper machine may even be destroyed which causes at least an interruption in the production, but usually it also requires reparations. The lint content in the paper machine room should at least not rise above the limits allowed by the health authorities. Removal of lint by cleaning the paper machine is a separate operation, which as such generates costs, and often also lengthens the production breaks. If the lint is removed with the aid of a water jet, this can cause additional problems as the equipment and structures get wet.
A number of solutions are known for reducing the linting problems in the region of a Yankee cylinder dryer and a roller. The publications U.S. Pat. Nos. 5,011,574 and 4,019,953 present equipment to be located close to the doctor blade, in order to remove the lint created just at that point. The publication WO 97/44525 shows a shaped suction box for sucking away lint from between the Yankee cylinder and the roller. The publications thus present some partial solutions, but they do not show an effective total solution for removing the linting problems.